President Donald Trump is set to reveal his decision on whether to keep the US in the Iran deal on Tuesday, a move that could determine the fate of the 2015 agreement that froze Iran’s nuclear program.

President Donald Trump is set to reveal his decision on whether to keep the US in the Iran deal on Tuesday, a move that could determine the fate of the 2015 agreement that froze Iran’s nuclear program.

The announcement is set to cap more than a year of deliberation and negotiation that has at time pitted the president against some of his closest aides and key American allies.

I will be announcing my decision on the Iran Deal tomorrow from the White House at 2:00pm.

Mr Trump is facing a self-imposed May 12 deadline over whether to uphold the 2015 nuclear agreement, which he has long criticised. He has signalled he will pull out of the pact by the deadline unless it is revised, but he faces intense pressure from European allies not to do so.

“I will be announcing my decision on the Iran Deal tomorrow from the White House at 2:00pm,” Mr Trump tweeted on Monday.

The president has been the subject of an intense lobbying effort by American allies to maintain the agreement, with British Foreign Minister Boris Johnson making a last-ditch appeal to the administration in a visit to Washington this week.

European leaders say that they are open to negotiating a side agreement with Iran, but the existing framework must remain untouched for that to happen.

Iranian President Hassan Rouhani has spoken out in favour of keeping the pact (Iranian Presidency Office/AP)

It is not immediately clear what Mr Trump will announce or whether he will announce the end of the deal or push for a renegotiation. In October he “decertified” the deal with Iran, but did not move to re-impose sanctions, known as a “snap-back”.

On Monday, Iranian President Hassan Rouhani said Iran would be willing not to abandon the nuclear deal even if the United States pulls out, providing the European Union offers guarantees that Iran would keep benefiting from the accord.

Mr Rouhani said that “what we want for the deal is that it’s preserved and guaranteed by the non-Americans” — a reference to other signatories of the 2015 agreement.

The United States does not need John Kerry’s possibly illegal Shadow Diplomacy on the very badly negotiated Iran Deal. He was the one that created this MESS in the first place!

Earlier on Monday, Mr Trump criticised John Kerry after reports that the former secretary of state has been promoting the Iran nuclear deal.

He said on Twitter: “The United States does not need John Kerry’s possibly illegal Shadow Diplomacy on the very badly negotiated Iran Deal. He was the one that created this MESS in the first place!”

Mr Kerry, who was also the lead negotiators for the Obama administration on the Paris climate accord, has been promoting both agreements since he left office.

The Boston Globe reported on Friday that Mr Kerry, the lead negotiator on the deal for the Obama administration, had been privately meeting with foreign officials to strategise on how to keep the US in the deal.